(1) Field of the Invention
The present invention relates to the exercise of control over the delivery of solid material to the interior of a pressurized vessel and particularly to the controlled delivery of charge material to the interior of an operating shaft furnace. More specifically, this invention is directed to apparatus for controlling the rate of flow of material being directed onto the hearth of a furnace and flowing under the influence of gravity. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
The present invention is particularly well suited for use in a furnace charging installation of the type disclosed in U.S. Pat. No. 3,693,812 wherein a charge distribution member, in the form of a chute or spout, is supported for rotation in the throat of the furnace and is angularly adjustable relative to the longitudinal axis of the furnace. In the operation of a blast furnace, one of the parameters which is desirably controlled by the furnace operator is the profile of the charge material which is deposited upon the furnace hearth. The charge material profile may be accurately controlled through the exercise of control over the orientation of the distribution member of U.S. Pat. No. 3,693,812 and by exercising control over the rate at which the charge material is supplied to the distribution member. In order to permit continuous furnace operation, the material with which the furnace is to be charged will be temporarily stored in a sealable vessel positioned above the furnace throat, this intermediate storage vessel being alternately depressurized for loading and pressurized through a level of the furnace pressure for unloading into the furnace. When released from the temporary storage vessel, the furnace charge material will travel downwardly, under the influence of gravity, and will be guided through channels to the upper end of the charge distribution member. A metering device, to control the rate of flow of charge material, will be located along the flow path between the temporary storage vessel and the distribution member, the metering device being physically positioned above the top of the furnace to facilitate installation and service.
A prior art charge metering or flow control device of the type generally described above is disclosed in U.S. Pat. No. 4,074,835. It is to be noted that, in the prior art, the metering device has been installed in a channel or passage which was angularly inclined with respect to the furnace axis. The angularly inclined channel directed the charge material from the temporary storage vessel to the upper end of a vertically oriented feed channel which had its discharge end aligned with the upper end of the distribution member within the furnace.
The incorporation of the metering device in a channel or passage which is angularly oriented with respect to the furnace axis has precipitated a number of problems. For example, the rate of flow of the charge material was not uniform across the channel and, because of the angular orientation of the channel, the charge material did not fall vertically and symmetrically onto the uppper end of the distribution member. Previous attempts to solve these problems, to thereby permit more precise control of the furnace charging procedure, have included the installation of guide blades in the path of the charge material, was suggested in copending U.S. application Ser. No. 306,950, filed Sept. 30, 1981 and assigned to the assignee of the present invention, or the use of a tubular plug in the charge material flow path as suggested in U.S. Pat. No. 4,040,530. These previously proposed solutions to the problem of insuring a vertical and symmetrical flow of charge material at the upper end of the distribution member, which have not proved to be totally successful, constitute an effort to simulate the conditions which would exist if the intermediate storage vessel and its discharge orifice were coaxial with the furnace axis.
In prior furnace charging installations it was deemed impossible to locate the intermediate storage vessel on the furnace axis. One of the primary causes of this inability is the fact that, in order to enhance furnace operating efficiency, at least a pair of storage vessels were associated with each furnace. This arrangement has permitted the loading of one vessel during the period of time that the other vessel was discharging its contents into the furnace. Obviously, when a pair of juxtaposed temporary or intermediate storage vessels are employed, they cannot both be located on the furnace axis. Secondly, the metering devices presently available require, for operation, that the moving stream of solid charge material be penetrated at an oblique angle in order to reduce flow rate. Accordingly, even in those charging installations where a single intermediate storage vessel was utilized, for example an installation of the type shown in allowed copending application Ser. No. 62,969 filed Aug. 2, 1979, now U.S. Pat. No. 4,322,197, the storage vessel was located such that its axis was parallel to rather than coaxial with the furnace axis.